Consumers have to shell out a collective $4.1 billion to freeze their credit reports and prevent fraudsters from using personal information possibly exposed in the massive data breach at Equifax, according to new research from advocacy group U.S. PIRG.

The data show that with only eight U.S. states requiring that credit freezes — which prevent lenders from accessing your credit report — be offered free of charge, about 158 million consumers between ages 18 and 65 would face a hefty tab.

"Consumers can't control access to their own credit reports without paying a fee, which is outrageous," said Mike Litt, consumer advocate for U.S. PIRG.

"We're not customers" of the credit-reporting firms, he added. "We don't get to choose them collecting and selling our information — and, in the case of Equifax, losing it — and we have to pay a fee to protect it?"

(Click on the interactive map below to check fees in your state.)

Source: U.S. PIRG

The data come as a round of congressional hearings start Tuesday to grill former Equifax CEO Richard Smith — who retired last week — about the company's massive data breach, which potentially put the personal data of as many as 145 million consumers in the hands of criminals.

Also making the rounds on Capitol Hill are several bills that would make credit freezes free in all states, although it's unclear at this point whether they will gain any momentum with only Democratic backers in a Republican-controlled Congress.

Data exposed in the breach, which Equifax said was discovered July 29, include names, birth dates, Social Security numbers, addresses and some driver's license numbers. The cyberattack occurred from mid-May through July and was revealed by the company in early September.

Kevin Lamarque | Reuters

Richard Smith, former chairman and CEO of Equifax Inc., testifies before House Energy and Commerce hearing on "Oversight of the Equifax Data Breach: Answers for Consumers" on Capitol Hill in Washington, U.S., October 3, 2017.

Experts say all consumers should assume their information was compromised. Just yesterday, the number of consumers potentially affected in the breach was revised upward.

The basic benefit of freezing your credit report is that if a scammer attempts to take out a loan or establish credit using your personal information, the lender will be unable to check your credit score or history and generally won't approve the application.

Yet to do so costs anywhere from $2 to $10 in the states where freeze fees are charged. In some states, you'll also pay a fee to unfreeze your report when you need a lender to approve a valid application. Also, some states waive the fees for certain consumers, such as seniors or active-duty military members.

"Consumers can't control access to their own credit reports without paying a fee, which is outrageous."-Mike Litt, consumer advocate at U.S. PIRG

Equifax is offering all consumers free credit-monitoring for a year, with a signup deadline now set for Jan. 31, 2018. The service includes free freezes.

The company also says it will begin offering a free lifetime credit lock service to consumers in January, although few details are available yet.

The problem with that, say advocates, is it still leaves fees at the other two major credit-reporting firms, TransUnion and Experian.

Litt said his group is working on how to make the legislation to remove all fees something that lawmakers of all stripes can get behind.

"Of all the things that need to be worked on [related to credit firms], this is one idea for which there should be overwhelming bipartisan support," Litt said.